Each type of grain has a different weight per bushel. IE shelled corn 56lbs soybeans 60lbs wheat 60lbs. check out this chart http://extension.missouri.edu/publications/DisplayPub.aspx?P=G4020
Boxcar capacity is limited by weight, grain will not cube out a boxcar. Figure 750 bushels of corn in a typical 40t boxcar. About 700 bushels of soybeans or wheat. Use the above table for other calculations. A modern grain semi-trailer at legal weight limit will hold 800-900 bushels. But full capacity is 1100-1200 bushels for many trailers, well over the legal weight limit, esp if the moisture is high.
Another reason small elevators disappeared: farm trucks and wagons got to big to fit inside the covered unloading bays. Most old wooden elevators were built in the days of wagons and smaller single axle trucks and the unloading building openings were sized accordingly. They could not handle the large dual axel trucks, semi’s, or the mega sized farm wagons.
Doug Harding
www.iowacentralrr.org